Pumping apparatus for evacuated envelopes



March 18, 1958 A. F. FENGLER ETAL, 3 m

PUMPING APPARATUS FOR EVACUATED ENVELOPES Filed 001:. 26, 1954 I 3 Sheets-Sheet l INVENTORS ALBERT F. FENGLER FIG I FRED MMACKEY ATTORNEYS.

March 18, 1958 A. F. FENGLER EI'AL 2,827,080

PUMPING APPARATUS FOR EVACUATED ENVELOPES Filed 001:. 26, 1954 3 Sheets-Sheet 2 INVENTORS ALBERT F. FENGLER FRED M. MACKEY BY ATTORNEYS March 18, 1953 A. F. FENGLER ETAL 2,827,080

PUMPING APPARATUS FOR EVACUATED ENVELOPES Filed 001:. 26, 1954 3 Sheets-Sheet 3 ALBERT F. FENGLER BY FRED M. MACKEY- waKnfiliu ATTORNEYK United States Patent PUMPING APPARATUS FOR EVACUATED ENVELOPES Albert F. Fengler, Norwalk, and Fred M. Mackey, Springdale, Conn., assignors to Machlett Laboratories, incorporated, Springdale, Comm, a corporation of Connecticut Application October 26, 1954, Serial No. 464,738

9 Claims. (Cl. 141-65) This invention relates to a structural arrangement for the protection of an exhaust tubulation connecting an envelope to be evacuated and a vacuum pump.

In the prior art, damage has occurred on occasion to the exhaust tubulation, or to envelope portions adjacent the exhaust tubulation, of a vacuum envelope during the final stages of manufacture. Ordinarily this damage consists of rupture of the tubulation, or of the envelope portion adja out the tubulation. If such rupture occurs to the tubulation in an electron. tube, for example, the resulting contamination of parts will make reprocessing of the tube necessary and may render the tube useless. If the rupture occurs while the tube is being heated for outgassing purposes, the contamination of the elements may even destroy their salvage value. The situation is serious, particularly in the case of large tubes, because at this final stage of manufacture, the long hours of labor required to process parts and build and process a tube have already been expended, and almost the full value of the finished product is at stake.

Our analysis has indicated that breakage of the exhaust tubulation frequently occurs while the vacuum envelope is still attached to the vacuum pump or when detaching it from the pump. The difliculty arises because of the necessity of making the connection between the vacuum envelope and the pump vacuum tight, which construction necessitates the use of rigid materials. In view of the rigidity of the tubulation, its small diameter constitutes a structural weakness. However, for the sake of convenience and economy it would be impractical to make the connection between the envelope and the pump of large size and of sturdy construction.

In general the structural weakness of the exhaust tubulation has proved most dangerous on two distinct occasions. One dangerous period occurs during the outgassing of an electron tube while connected to the vacuum pump. During that time expansion effects cause the tube to move off its support. Once the tube is off its support only the exhaust tubulation is left to support the tube so that extraordinary strains are imposed on the tubulation. The other dangerous period occurs during severance of the connection between. the vacuum pump and the envelope. In the course of the severing process, elongation of the connection member which is being severed occurs when the connection member is necked. With metal tubulations, such elongation will force the tube upward off its support and leave the exhaust tubulation supporting the tube in a manner quite similar to the way in which the tubulation is left to support the tube as a result of expansion effects during outgassing. When severing glass tabulations, the glass blower advantageously moves the tube away from the pump in order to obtain a satisfactory seal, and since this movement is effected manually, it is apt to impose strains upon the tubulation.

The present invention makes it possible for an electron tube to remain firmly on its supporting platform during its outgassing, despite the usual accompanying expansion effects, and therefore the pinch off or seal off of the "ice exhaust tubulation can be efiected without the danger of breakage which normally accompanies the removal of the tube from its supporting platform.

More specifically, the present invention is a structural arrangement for the protection of an exhaust tubulation connecting an envelope to be evacuated and a vacuum pump. The structural arrangement incorporates and is arranged on a frame which includes a support for the envelope to be evacuated. The high vacuum system is connected to the envelope to be evacuated by rigid connection means including the exhaust tubulation on the vacuum envelope. Then, in order to give the structural arrange.- ment the flexibility which we have found to be necessary to prevent the exhaust tubulations rupture, the vacuum system is mounted on a support which is movable relative to the frame. The movable support permits counteraction of expansion effects and other elongation effects. Furthermore the movable support is subject to voluntary movement to aid in the severance of the exhaust tribulation.

For a better understanding of the present invention reference is made to the following drawings:

Fig. 1 is a partially schematic side elevational view of the present invention showing its supporting frame structure in section and the rest of the structure in elevation;

Fig. 2 is a schematic representation similar to Fig. 1 illustrating a common prior art construction of apparatus for evacuating a vacuum envelope;

Fig. 3 is a more detailed view of part of the structure of the present invention showing specifically the high vacuum system and the support structure for the high vacuum system;

Fig. 4 is a partial sectional view taken along line 4-4 of Fig. 3 from above the high vacuum system of the present invention.

Referring to Fig. l, a structural arrangement for the protection of an exhaust tubulation connecting an envelope to be evacuated and a vacuum pump is illustrated somewhat schematically. The vacuum envelope is shown connected into the high vacuum pump portion of the structural arrangement. In this instance the vacuum envelope is electron tube 10. The vacuum pump is generally designated 11. The mounting frame is generally designated 12. The mounting frame may have many forms, and in this instance it is shown as a shelf-like support structure having sidewalls 13, a bottom support shelf 14, an intermediate support shelf 15 and an envelope supporting shelf 16. The sidewalls of the structure provide legs which rest on ground 17.

The connection means between the vacuum pump 11 and the envelope it) is made through rigid tubing 20 to the exhaust tribulation 21 of the vacuum envelope.

The support means 24 for the high vacuum system is preferably a member which is movable relative to another member 25 which is mounted on the frame 12. In addition, a spring-like connection means 26 is provided between the support means 24 or some portion of the high vacuum system and the frame 12. Thus provision is made for relative motion in the vertical direction between the pump support means and the supporting portion of the frame.

Referring now to Fig. 2, a schematic representation of exhaust equipment is shown. In Fig. 2 the number designations correspond to those in Fig. l with the addition of primes thereto. Generally speaking, in the prior art it was common to provide a rigid connection 24' between the high vacuum portion ill of the pump system and its support. The high vacuum system was also rigidly connected to the vacuum envelope it). This rigid connection consisted of the glass tubulations 2'8 and the exhaust tribulation 21' on the vacuum envelope itself.

During the course of the pumping operation, an electron tube 10' is bakedat high temperatures in order to 3 n thoroughly outgas the vacuum envelope and the electrodes and other parts which it contains. During its heating, expansion occurs in the electron tube and in its connection to the high vacuum system. This expansion has resulted in the undesirable situation shown 'in Fig. 2, i. e., the vertical movement of the vacuum envelope off its support 16, because of the rigid connectionof the high vacuum system to the frame. In this precarious position with only the small diameter exhaust tubulation to .support the envelope, as has happened on occasion, any sudden lateral force may cause rupture of the exhaust tubulation or adjacent envelope portions.

By contrast, using the structural arrangement illustrated in Fig. l,during the outgassing of envelope 10, the expansion which occurs will be taken up by the. movable support 24 for the high vacuum system. Because'support means 24 for the pump system is movable, the envelope 10 will remain firmly on its support 16 while the expansion effects are absorbed by the downward movement of the pump system. 1.

In the prior art, in the course of severing a metallic exhaust tubulation, the necking" of the tubulation due .to the .efiective elongation of the tubulation during its pinching has also caused the vacuum envelope 10 to be raised above its supporting platform 16 in a manner similar to that shown in Fig. 2. As in the case of the problem during outgassing, the exhaust tubulation ofa vacuum envelope in this position is subject to damage. Furthermore, the very application of pressure necessary to cause the severance of the exhaust tubulation may produce such damage. However, again the structural arrangement of the present invention permits the effective elongation of the tubulation to be absorbed by the downward movement of the high vacuum pump system so that the envelope may remain firmly on its support throughout the severing process.

When a glass exhaust tubulation is employed, the severing process is one of heating the glass tubulation until it becomes soft enough to yield to atmospheric pressure. Atthis point the glass closes in on itself in the heated region to form the necessary vacuum tight seal ofi, and the envelope is pulled away from the pump system to sever the tubulation. However, the severing problem has been complicated by the advent of large tubes which are not conveniently lifted or otherwise moved away from .the high vacuum system. It is dangerous and clumsy to move a heavy tube to sever its exhaust tubulation, but even with smaller tubes random forces brought to bear onthe tubulation while pulling the envelope away from thepump may damage the tubulation.

The structural arrangement of the present invention .makes it unnecessary to pull the envelope away from the pump in severing a glass tubulation. Instead, using the present invention, the'pump may be pulled away fromthe envelope. This may be done after sealing the high vacuum system to the envelope at or near the uppermost position of the vacuum system relative to the frame. Thus a long downward travel distance for the support for the vacuum system is available. Then, during the severing operation, the support for the high vacuum system is moved downward so that the envelope is permitted to remain on its supporting platform 16 throughout the severing process.

Referring now to Figs. 3 and 4, the movable support structure and the vacuum systemare illustrated in more detail. Diffusion pump 11 and the cold trap 30 are interconnected by tubing generally designated 31. The difthe cold trap. A supportingrframe 12 isprovided and platforms 14 and 15 are specifically arranged to support both above and below support member 24. Support member 24 is advantageously tubular in shape, although it may be variously shaped, and itis advantageously mounted to surround shaft 25, which is'aflixed to portions 14 and 15 of the frame 12 at its oppositeends; V Interconnection between portions of the frame 12 and shaft 25 may be accomplished in-a variety of ways.

Movement is facilitated between movable supporting member 24 and shaft 25 by linear-ball bushings 35.

" which are affixed to opposite ends of the tubular sup fusion pump 11 is, in turn, connected to a fore pump (not shown) and the vacuum trap 30 is, in turn, connected through tubulation 20 to the envelope to be evacuated.

In the preferred construction shown in Figs. 3 and 4, support brackets 33 are provided to connect the difiusion pump'to supportmember 24. Support bracket 34 is employed to support the interconnecting tube 51 adjacent 75 These ball bushings are housed in bracket members 36 porting member 24. The linear ball bushings 35 may-then be held in place within 'the bracket members 36 by means such as snap rings 53 which may be inserted into the open ends of the members 36 adjacent the ends of the bushings35. r Iv The bearing surface adjacent eachend of the member 24 may be protected by the use of .a dust boot or cover 37 of a bellows type made of one of the syntheticrrub ber products. One end of each of these boots is connected to the adjacent end of shaft 25 by anannularmember 38 which is fixed to the shaft. The other end of eachof these boots is advantageously provided with means such asa snap ring 54 which resiliently'fits into an annular circumferential groove. in the bushing housing 36 with which it cooperates'whereby each boot 37v is attached to a respective bracket member 36. i j

it is desirable that the movable structure be counterbalanced so that whatever position is selected for it, it

of these springs is mounted on spools 40 and 41 at its opposite ends. The spools 40 at the lower ends are mounted on cross-piece 42 which also carries support member 34. Spools 41 at the opposite ends ofthe springs 26 are rotatable about an axis supported between mounting brackets 44. s

Other items mustbe or may be mounted upon support member 24. For instance, a DeWar flask containing liquid air for cooling the cold trap .30 may be supported on this member by bracket 46 which carries an annular padded ring 47 below the cold trapfor supporting the flask. Bracket 49 may be used tosupport vacuum gauge 50 which may or may not bemounted on this movable structure.

i As shown in Fig. 1 glass neck 20 issealed to aglass or metal exhaust tubulation21 on the envelope 10 to be evacuated. The envelope is supported on a platform or shelf 16 on the frame 12. At the other end of the vacuum system, a connection is made between diffusion pump 11 and a mechanical fore pump (not shown). which produces a suflicient'vacuum to make the diffusion pump operable. This connection may be made through flexible rubber vacuum tubing; Electrical connections for diffusion pump heaters are made with'fiexiblewires. and the cooling system 52 is coupled to a watersupply through rubber hose or other such flexible coupling: c

In operation, this pump system works asdoes anyconventional pump system. First a lowtvacuum of about 10- mm. of mercury is pumped by'theffore pump. Thereafter, the diffusion pump 10 produces a'vacuumm the order of 10- mm. of mercury. The diffusion pump produces a high vacuum'in a manner well known to the art by the use of oilparticles, .or the like, to. remove an molecules from the system- The cold trap functions to condense water vapor and other deleterious material and also to' prevent oil vapors from the diffusion pump from tem. For instance, a mercury ditfusion pump may be substituted for the oil diffusion pump. The fore pump may be mounted on the movable support or it may be mounted on the frame and connected by flexible vacuum tubing to the diffusion pump. Various types of fore pumps may be employed. In fact, any modifications in the pump system consistent with the practice of the art is possible within the scope of the present inventions.

The frame, and particularly the support for the vacuum envelope, may take a great many forms, the forms illus trated being merely by way of example. The envelope itself need not be the envelope of an electron tube but may be any other envelope which requires a high degree of vacuum.

Various other modifications of the invention will occur to those skilled in the art. All such modifications within the scope of the claims are intended to be within the scope and spirit of the present invention.

We claim:

1. Apparatus of the character described comprising a frame having an immovable support for supporting an envelope having an exhaust tubulation, a fixed guide member mounted on the frame, a movable support mounted on and movable along the guide member toward and away from an envelope supported on the immovable support, a pumping system mounted on and movable with the movable support, the pumping system having a portion adapted to be rigidly joined integrally to the exhaust tubulation of an envelope on the immovable support, and restraining means connected to the movable support and yieldably retaining the movable support and pumping system thereon in adjusted position relative to the guide member and envelope.

2. Apparatus of the character described comprising a frame having an immovable shelf for supporting an envelope having an exhaust tubulation, a fixed shaft carried by the frame and extending substantially normal to the shelf, a tubular support mounted on and movable longitudinally of the shaft, a pumping system mounted on and movable with the tubular support, the pumping system having a portion adapted to be sealed directly and rigidly to the exhaust tubulation of an envelope on the shelf, and restraining means connecting the tubular support t the frame and yieldably retaining the tubular support in adjusted position on the shaft and simultaneously yieldably retaining the pumping system in adjusted position relative to the envelope.

3. A structural arrangement for the protection of an exhaust tubulation of an envelope to be evacuated comprising, a frame having a shelf portion for supporting the envelope to be evacuated, a high vacuum pump system adjacent the shelf portion, substantially rigid connection means connecting the exhaust tubulation on the envelope to be evacuated to the high vacuum pump system, a shaft carried by the frame, a support of tubular form coaxially surrounding the shaft and carrying the pump system, bearings coupling the support to the vertical shaft and permitting longitudinal movement of the support on the shaft, and counterbalancing means connected between the frame and the support to maintain adjusted position of the support relative to the shaft.

4. A structure as described in claim 3 in which the bearings permitting longitudinal movement of the support are a pair of frictionless bearings located at opposite ends of the support, and the hearings have protective flexible covering members mounted thereover, said covering members extending between the tubular support and the shaft at both ends of said support.

5. A structure as described in claim 3 in which the counterbalancing means embodies spring means which are capable of exerting the same amount of pull at all positions of the support, said pull being just sufficient to counterbalance the effect of gravity on the support and structure thereon.

6. Pumping apparatus for evacuating envelopes having exhaust tubulation means, said apparatus comprising a first support adapted to support an envelope independently of the exhaust tubulation means thereon, a second support spaced from the first support, a pumping system on the second support for evacuating said envelope, and rigid connection means for connecting the pumping system to the exhaust tubulation means of the envelope independently of said supports, at least one of said means being capable of elongation, one of said supports being automatically adjustable in a direction toward and away from the other support in response to such elongation whereby the spacing between the pumping system and envelope will be varied to the extent of the elongation.

7. Pumping apparatus for evacuating envelopes having exhaust tubulations, said apparatus comprising a pumping system, a fixed support adjacent the pumping system for supporting an envelope to be evacuated independently of the exhaust tubulation thereon, a support for the pumping system, and rigid connection means for connecting the pumping system to the exhaust tubulation of the envelope independently of the supports, at least one of connection means and exhaust tubulation being capable of elongation, said pumping system and support on which it is carried being automatically adjustable toward and away from the other support in response to such elongation whereby the spacing between the pumping system and envelope will be varied to the extent of the elongation.

8. Pumping apparatus for evacuating envelopes having glass exhaust tubulations, said apparatus comprising a fixed shelf adapted to support an envelope independently of the tubulation thereon, a support s aced from the shelf, a pumping system on the support for evacuating said envelope, and a glass connection connecting the pumping system to the exhaust tubulation independently of the shelf and support, the support being movable with the pumping system thereon in a direction toward and away from the shelf whereby the length of the joined connection and tubulation may be varied while retaining the envelope in initial position on the shelf.

9. Pumping apparatus for evacuating envelopes having glass exhaust tubulations, said apparatus comprising a fixed shelf adapted to support an envelope independently of the tubulation thereon, a support spaced from the shelf, a pumping system on the support for evacuating said envelope, a glass connection connecting the pumping system to the exhaust tubulation independently of the shelf and support, the support being movable with the pumping system thereon in a direction toward and away from the shelf whereby the length of the joined connection means and tubulation may be varied while retaining the envelope in initial position on the shelf, and restrain ing means connected to the support and yieldably retaining the support and pumping system in adjusted position.

References Cited in the file of this patent UNITED STATES PATENTS 355,714 Reinmann Jan. 11, 1887 1,651,865 Blake et al. Dec. 6, 1927 1,728,034 B01 Sept. 10, 1929 

